Projection Stereolithography 3D Printing High-Conductive Hydrogel for Flexible Passive Wireless Sensing.

Hydrogel-based electronics have inherent similarities to biological tissues and hold potential for wearable applications. However, low conductivity, poor stretchability, nonpersonalizability, and uncontrollable dehydration during use limit their further development. In this study, projection stereolithography 3D printing high-conductive hydrogel for flexible passive wireless sensing is reported. The prepared photocurable silver-based hydrogel is rapidly planarized into antenna shapes on substrates using surface projection stereolithography. After partial dehydration, silver flakes within the circuits form sufficient conductive pathways to achieve high conductivity (387 S cm-1). By sealing the circuits to prevent further dehydration, the resistance remains stable when tensile strain is less than 100% for at least 30 days. Besides, the sealing materials provide versatile functionalities, such as stretchability and shape memory property. Customized flexible radio frequency identification tags are fabricated by integrating with commercial chips to complete the accurate recognition of eye movement, realizing passive wireless sensing.

A 4D Printed Adhesive, Thermo-Contractile, and Degradable Hydrogel for Diabetic Wound Healing.

Chronic wound healing remains a substantial clinical challenge. Current treatments are often either prohibitively expensive or insufficient in meeting the various requirements needed for effective diabetic wound healing. A 4D printing multifunctional hydrogel dressing is reported here, which aligns perfectly with wounds owning various complex shapes and depths, promoting both wound closure and tissue regeneration. The hydrogel is prepared via digital light process (DLP) 3D printing of the mixture containing N-isopropylacrylamide (NIPAm), curcumin-loaded Pluronic F127 micelles (Cur-PF127), and poly(ethylene glycol) diacrylate-dopamine (PEGDA575-Do), a degradable crosslinker. The use of PEGDA575-Do ensures tissue adhesion and degradability, and cur-PF127 serves as an antibacterial agent. Moreover, the thermo-responsive mainchains (i.e., polymerized NIPAm) enables the activation of wound contraction by body temperature. The features of the prepared hydrogel, including robust tissue adhesion, temperature-responsive contraction, effective hemostasis, spectral antibacterial, biocompatibility, biodegradability, and inflammation regulation, contribute to accelerating diabetic wound healing in Methicillin-resistant Staphylococcus aureus (MRSA)-infected full-thickness skin defect diabetic rat models and liver injury mouse models, highlighting the potential of this customizable, mechanobiological, and inflammation-regulatory dressing to expedite wound healing in various clinical settings.

Repeatedly Recyclable 3D Printing Catalyst-Free Dynamic Thermosetting Photopolymers.

Photo-curing 3D printing technology has promoted the advanced manufacturing in various fields, but has exacerbated the environmental crisis by the demand for the chemically cross-linked thermosetting photopolymers. Here, the authors report a generic strategy to develop catalyst-free dynamic thermosetting photopolymers, based on photopolymerization and transesterification, that can enable users to realize repeatable 3D printing, providing a practical solution to the environmental challenges. That the ß-carbonyl group adjacent to the ester group greatly accelerates the rate of transesterification is demonstrated. The generated resins from the immobilization of the catalyst-free reversible bonds into the photopolymers leads to a dynamic covalently crosslinked network structure upon UV based 3D printing, which exhibit controllable mechanical properties with elastomeric behaviors to thermadapt shape memory polymers. Furthermore, the resulting network can be reverted into an acrylate-functioned photopolymer that is suitable for 3D printing again, presenting an on-demand, repeatedly recyclable thermosetting photopolymer platform for sustainable 3D printing.